Subduction zone fluids, namely aqueous solution, hydrous melts, or supercritical fluids, are key agents for mass transfer and element exchange between the subducting slab and the overlying mantle wedge. The fluid processes and related geochemical effects greatly affect the geochemical composition of the subducted slab, the overlying mantle wedge, and its derived arc magmas, which thus play a vital role in the secular evolution of Earth’s crust-mantle system.
The fluid process in subduction zones is controlled by protolith composition, geothermal structure, specific pressure-temperature conditions, and fluid-rock interaction processes. In a cold subduction zone, aqueous solution would dominate, which mainly carries fluid mobile large ion lithophile elements (LILEs). When the temperature increases, partial melting of subducting crust can occur that forms hydrous melts. This type of fluid exhibits elevated transport capacity of LILEs and light rare earth elements (LREEs). With increasing P-T conditions, supercritical fluids can occur when the rock system exceeds the second critical endpoint. Current studies have shown that supercritical fluids can carry much higher contents of LILEs, LREEs, and high-field strength elements (HFSEs) in comparison to aqueous solution and hydrous melts. However, due to the complexity of subduction zones and fluid-rock systems, the detailed fluid processes, and the associated elemental and isotopic composition of subduction zone fluids are still not well known. This is particularly true for supercritical fluids.
In this Research Topic, we would like to address the following research questions:
(1) Controlling factors of metamorphic dehydration and partial melting in subduction zones, e.g., the impacts by protolith composition, thermal structure of subduction zones, differences in P-T path, and fluid-rock interaction processes during fluid migration;
(2) Conditions and mechanisms of partial melting in oceanic and continental subduction zones, and how they affect the geochemical composition of resultant partial melts;
(3) Conditions and geochemical composition of supercritical fluids in various rock systems;
(4) Impacts of metamorphic dehydration and partial melting on element mobility and isotopic fractionation in subduction zones, the elements include LILEs and volatile elements like C-H-N-S;
(5) Differences of metamorphic dehydration and partial melting between oceanic subduction zones and continental subduction zones;
(6) Relationship between fluid action, element mobility, and crust-mantle interaction at the slab-mantle interface as well as subduction zone magmatism.
Contributions underlining such cross-disciplinary problems will significantly advance our understanding of fluid processes and related geochemical behaviors in subduction zones. This Research Topic welcomes Original Research Articles and Reviews in the following directions:
• Conditions and processes for metamorphic dehydration or partial melting of subducting slab in oceanic subduction zones and continental subduction zones
• Estimation regarding geochemical composition of subduction zone fluids based on natural rocks, high pressure-high temperature experiments, or theoretical calculations
• Element mobility and stable isotope fractionation associated with the action of subduction zone fluids
• Geochemical effects of subduction zone fluids on subducting slab, mantle wedge, and arc magmas
Subduction zone fluids, namely aqueous solution, hydrous melts, or supercritical fluids, are key agents for mass transfer and element exchange between the subducting slab and the overlying mantle wedge. The fluid processes and related geochemical effects greatly affect the geochemical composition of the subducted slab, the overlying mantle wedge, and its derived arc magmas, which thus play a vital role in the secular evolution of Earth’s crust-mantle system.
The fluid process in subduction zones is controlled by protolith composition, geothermal structure, specific pressure-temperature conditions, and fluid-rock interaction processes. In a cold subduction zone, aqueous solution would dominate, which mainly carries fluid mobile large ion lithophile elements (LILEs). When the temperature increases, partial melting of subducting crust can occur that forms hydrous melts. This type of fluid exhibits elevated transport capacity of LILEs and light rare earth elements (LREEs). With increasing P-T conditions, supercritical fluids can occur when the rock system exceeds the second critical endpoint. Current studies have shown that supercritical fluids can carry much higher contents of LILEs, LREEs, and high-field strength elements (HFSEs) in comparison to aqueous solution and hydrous melts. However, due to the complexity of subduction zones and fluid-rock systems, the detailed fluid processes, and the associated elemental and isotopic composition of subduction zone fluids are still not well known. This is particularly true for supercritical fluids.
In this Research Topic, we would like to address the following research questions:
(1) Controlling factors of metamorphic dehydration and partial melting in subduction zones, e.g., the impacts by protolith composition, thermal structure of subduction zones, differences in P-T path, and fluid-rock interaction processes during fluid migration;
(2) Conditions and mechanisms of partial melting in oceanic and continental subduction zones, and how they affect the geochemical composition of resultant partial melts;
(3) Conditions and geochemical composition of supercritical fluids in various rock systems;
(4) Impacts of metamorphic dehydration and partial melting on element mobility and isotopic fractionation in subduction zones, the elements include LILEs and volatile elements like C-H-N-S;
(5) Differences of metamorphic dehydration and partial melting between oceanic subduction zones and continental subduction zones;
(6) Relationship between fluid action, element mobility, and crust-mantle interaction at the slab-mantle interface as well as subduction zone magmatism.
Contributions underlining such cross-disciplinary problems will significantly advance our understanding of fluid processes and related geochemical behaviors in subduction zones. This Research Topic welcomes Original Research Articles and Reviews in the following directions:
• Conditions and processes for metamorphic dehydration or partial melting of subducting slab in oceanic subduction zones and continental subduction zones
• Estimation regarding geochemical composition of subduction zone fluids based on natural rocks, high pressure-high temperature experiments, or theoretical calculations
• Element mobility and stable isotope fractionation associated with the action of subduction zone fluids
• Geochemical effects of subduction zone fluids on subducting slab, mantle wedge, and arc magmas
